Recently, either a solid state drive (SSD) or a hard disk drive (HDD) is chosen as a storage device depending on the application. The biggest advantage of the SSD is the fast data transfer rate. On the other hand, the cost per unit of capacity is high and the number of rewrites is limited. Thus, the HDD is superior to the SSD in some points. Therefore, it is expected that users will choose and use a HDD as a storage device if they need frequent access and large capacity.